The Analytical Core will serve as a resource and service for carrying out all laboratory analyses related to Projects l, Il and Ill in this proposal. The core has developed and validated sample collection and preparation procedures for blood, fecal, mononuclear cells, tissue blocks, and rectal biopsies and will continue to optimize methods for measuring the surrogate endpoint biomarkers (SEBs) to be used in the three projects within this proposal. Endpoints to be analyzed by the Analytical Core will include blood and fecal bile acids, cell proliferation measured by proliferating cell nuclear antigen (PCNA), protein kinase C (PKC) enzymatic activity and isotype expression in rectal mucosal biopsies, and DNA ploidy in adenomatous polyps. The Analytical Core will oversee and coordinate the collection and processing of all samples related to this Program Project at the various participating hospitals and clinics. In addition, the Analytical core will be responsible for the training of personnel involved in the collection and processing of study samples. It will perform actual assays and will work closely with the Biometry Core (B) to provide data for reporting and interpretation. Quality assurance and quality control procedures will continue to be developed by the Analytical Core which will be supervised by the Biometry Core for sample acquisition, processing, and Core which will be supervised the Biometry Core for sample acquisition, processing, and analysis procedures included in each of the clinical projects.